Germany’s top manufacturers agreed to recall 630,000 vehicles to tweak diesel engine software technology blamed for causing high pollution. Volkswagen, Opel, Audi and Mercedes diesel cars will be recalled to fix engine management systems, a German government official said.

BMW, which invested in fuel saving technologies earlier than most rivals, was not part of the recall, the official said.

Diesel engines have come under scrutiny ever since the VW dieselgatewhich has triggered rigorous controls by various government entities around the world. European tests have found several carmakers using a legal loophole allowing them to throttle back emissions treatments under certain circumstances, ostensibly to protect engines. German motor transport authority KBA questioned this technique on several occasions.

Daimler said late Thursday the U.S. Department of Justice had asked it to investigate its emissions certification process for vehicles. “We cannot go into details,” Daimler finance chief Bodo Uebber told the press.

It was not immediately clear what had triggered the DoJ intervention.

Volkswagen said on Friday it would take a 16.2-billion-euro ($18.2 billion) hit to its 2015 results and slash its dividend to help pay for its emissions-test cheating scandal.